Reproduction apparatus having a buffer for reducing the mean access time to an information carrier

ABSTRACT

The invention relates to a reproduction apparatus having a buffer for reducing the mean access time to an information carrier which has for example a discontinuous data structure or a relatively long access time. For writing sectors to the buffer and for finding sectors in the buffer, a control table with a number of place holders and three variables is provided, the place holders in each case pointing with an index to a subsequent place holder in an endless chain of place holders which is divided into three regions, in which a predetermined sector in the order in the respective region is identified by one of the variables. Even though only one row of place holders is provided, multiple access to a plurality of sectors written to the buffer is made possible with a low outlay by means of the control table, so that the number of slower accesses to the information carrier is reduced and the mean access time is shortened. Application is envisaged for reproduction apparatuses with a small storage space, such as, for example, a DVD reproduction apparatus.

The invention relates to a reproduction apparatus having a buffer forreducing the mean access time to an information carrier which has forexample a discontinuous data structure or relatively long access time.

The speed of a reproduction apparatus or drive often directs attentionto a product. In the case of drives, in particular, faster also meanslouder and, on the other hand, very few drives actually achieve themaximum performance specified. Rather, what is more important forconvenient operation is the average speed or the mean access time duringthe reading of DVD and CD media which have a discontinuous datastructure or a relatively long access time. A drive which offersconstantly high speeds here will also reliably reproduce audio and videofiles. In CD applications, the read head often jumps from one sector toanother, for instance in order to load an intermediate sequence or themission briefing during playing.

The access time can be reduced with faster read heads, also referred toas pick-ups. However, they are expensive and lead to an improvement onlyto a limited extent.

Buffer technology, also referred to as caching, is known in computertechnology for reducing the mean access time or for accelerating thereproduction of a relatively slow storage medium. The cache is ahigh-speed buffer. It buffer-stores frequently used data stored onslower storage media. The effectiveness of the buffer is determined byits speed and the ratio in which data required by an application areavailable in the buffer and are found or still have to be retrieved fromthe slower storage medium. In principle, three types of buffers aredifferentiated:

In the case of a buffer which is also referred to as a direct mappedcache, each storage location is mapped on a single cache row which itshares with many other storage locations. Since there is only onepossible place where the storage location can be buffer-stored, there isno searching to be done and the cache row either does or does notcontain the storage information. Unfortunately, the direct mapped cache,which requires the least outlay, also has the poorest performance sincethere is only one place at which the address can be stored. The hit rateis relatively low since the requested data randomly have to be locatedat the first place in the row.

The fully associative cache has the best hit rate since each row in thecache can contain each address which is to be buffer-stored. This meansthat the problems occurring in the direct mapped cache disappear sincethere is not just a single row which an address has to use. However,this cache has the disadvantage that the cache has to be searched. Morelogic has to be added in order to determine which of the different rowsis to be used in order to add a new entry. Normally, an algorithm isused which proceeds from the row recently used the least in order todecide which cache row is to be used. This means, however, that theoutlay and the complexity of the system are increased. The third type ofbuffer—the multiway associative cache—is a compromise between the directmapped and associative caches. The cache is divided into sets of “N”rows—“N” is normally 2, 4, 8, . . . , and each storage address can bebuffer-stored in one of a plurality of rows. This improves the hit ratecompared with direct mapped caches, without carrying out an extensivesearch, since “N” can be kept low. Nevertheless, both in a plurality ofstorage rows and an increased outlay for the control are necessary.

Therefore, it is an object of the invention to provide a reproductionapparatus having a buffer for reducing the mean access time to aninformation carrier which has for example a discontinuous data structureor a relatively long access time, which apparatus both requires a lowoutlay and ensures a short mean access time.

This object is achieved by means of features which are specified in theindependent claim. Advantageous refinements are specified in dependentclaims.

In accordance with one aspect of the invention, a reproduction apparatusis proposed having a buffer which requires a low outlay for controllingthe buffer and which nevertheless reduces the mean access time and thenumber of accesses to the slower information storage medium. For thispurpose, a buffer is provided which is accessed by means of a row orseries of place holders, which are concatenated, and a small number ofvariables. The place holders are organized in a series or row and,nevertheless, access not just to the first sector, but rather access toa plurality of sectors in the buffer which were loaded from aninformation carrier into the buffer is made possible with just one rowof place holders and variables. The row of place holders can be providedtogether with the row of variables in an application memory or directlyin the buffer. In the case of the arrangement of the place holders inthe application memory, each place holder corresponds to a storagelocation in the buffer and the place holders form, with the row ofvariables, a control table which is used to write the sectors to thebuffer or read them from the buffer. The row of place holders isconstructed in such a way that the place holders comprise, asinformation, in each case the index of the next place holder, as aresult of which an endless chain is formed which is preferably dividedinto three regions. A variable respectively identifies an entry pointinto one of the regions. This entry point into the respective region isfor example the first sector in the respective region. However, in orderto reduce the jumps upon alteration of the index assigned to a placeholder, it is also possible to use a sector in the preceding region asentry point. The aforementioned regions are the region of sectors inuse, which are referred to as allocated sectors, the region of releasedsectors and the region of unallocated place holders. The sectors in thethree regions are sorted in the temporal order in which they weretransported into the cache or buffer. The present sector of a row partis thus the first sector of this row part. The sectors are sorted in thetemporal order in which they were read from the information carrier,i.e. the sector read last is the first sector in this region and thelast place holder in this region points to the first place holder in thefollowing region. The released sectors are likewise sorted according tothe time when these sectors were transmitted into the cache, e.g. ifthey were freed from allocation. The last sector which is accepted fromthe region of the allocated sectors into the region of the releasedsectors is then the first sector in the region of the released sectors.The last place holder in the region of the released sectors then pointsto the first place holder of the region of unallocated place holders.The unallocated place holders contain no sectors. In the region ofunallocated place holders, an arbitrary order is possible, but it mustbe ensured that the last sector in the region of unallocated placeholders points to the first place holder in the region of allocatedsectors, in order to form the endless chain provided.

In order to shorten the initialization of the row or chain of placeholders, it is provided that only the first next pointer is formedduring the writing of the first sector. As a result, the next placeholder to be allocated is already determined, so that initialization offurther place holders is unnecessary, as a result of which the timerequired for initialization is significantly shortened.

In order to control the abovementioned three regions of place holders,essentially three variables are required which, in the respectiveregion, identify a sector for entry into this region. However, in orderto prevent a non-unambiguous state from occurring by virtue of the factthat a plurality of variables access the same entry, it is provided thatthe variables are given the opportunity to show that they do notidentify any valid index value, or three further variables areadditionally provided, of which one of the three can be derived from theother two.

If an application requests a sector containing information of theinformation carrier, firstly a check is made to determine whether thesector with the corresponding sector number is already situated in thecache. If the sector with the corresponding sector number is alreadysituated in the cache, the buffer-stored sector is used, and if thecorresponding sector is not situated in the cache, it is read into thecache from the information carrier. For the sector read, an index in therow of place holders and the corresponding variable are then set in thecontrol table. This sector is identified as the present sector and it isallocated the first place holder in the region of allocated sectors. Ifthe cache is already allocated a sector in the region of allocatedsectors and unallocated place holders are still available, its index isused for the new sector and the index of the sector that was previouslyread in is increased by one, thereby preserving the endless chain ofplace holders. At the same time, the variable identifying the placeholder in the region is accordingly altered. Before the storage of thenew entry, the preceding place holder in the chain was the last placeholder in the region of unallocated sectors or, if there is no placeholder present in the region of unallocated sectors and at least onereleased sector is stored in the cache, the last sector, forming theoldest sector in the region of released sectors, is to be used. In otherwords, the last or oldest sector in the region of released sectors isphysically released in order to form a place holder for the new sector.

If place holders are not available either in the region unallocatedsectors or in the region of released sectors, in accordance with theprinciple of the chained place holders, the preceding place holder isused, which is the last place holder used in the region of allocatedsectors, i.e. the oldest allocated sector. If the applicationsubsequently desires an access to this sector, this sector must bereloaded.

This procedure is only practical if the application of the replaced oldallocated sector is able to recognize that the sector is no longerimmediately available, i.e. a reloading for a further sector access oran access to this sector constitutes an exception which automaticallyinstigates reloading of this sector.

If there is not enough memory available for allocating the row of placeholders, the cache is switched off and the sector number is readdirectly from the information carrier.

If a sector in the region of allocated sectors is released, it isshifted to the first place in the region of released sectors, the lengthof the regions adapting dynamically to the number of sectors in therespective region on account of the predetermined concatenation.

All insertion and movement functions require only a change in thecorresponding indices to the next place holders and a change in thevariables.

The disadvantages of the known types of buffer organization are avoidedby dynamically concatenated buffer regions, so that, despite a singlerow, it is possible to access a plurality of sector addresses in therow, thereby reducing the number of direct accesses to the informationcarrier and, as a result, the mean access time.

The term access time denotes the time between request and provision ofdata, and is generally specified in milliseconds. The mean access timedescribes the time required on average for finding and reading anarbitrary item of information on a storage medium.

The proposed solution can advantageously be employed for small memoriesand for apparatuses having long access times, such as, for example,drives for optical storage media which have read heads having a longaccess time, since sectors which are present in the cache or are writtento the cache upon request can be used directly from the cache withouthaving to be accepted into the memory. What is more, the control of thecache requires a low outlay. Furthermore, the size of the cache isadvantageously adapted to the storage space available in the memorysince the number of place holders adapts to the respective requirements.The mean access time for information carriers with discontinuous dataaccess or discontinuous data structure is reduced in particular byvirtue of the fact that a sufficient volume of data is kept in thebuffer and can be accessed directly without the need for returns to dataalready read from the information carrier. The number of accesses tosectors of optical storage media is reduced in the initialization phase,in particular by virtue of the fact that the so-called directory of filesystems is to be read out a number of times and the corresponding dataare made available by the buffer.

In the case of a recursive MP3 file search in an archive, by way ofexample, the entire directory tree of the storage medium is to besearched in its entirety, so that sectors already kept in the buffer canadvantageously be used and the number of accesses to the storage mediumand the number of read head returns are thereby reduced.

The corresponding sector number in the buffer is found in a known mannerby comparison of request and sector found. Since a search in theconcatenated buffer is significantly faster than the access to theinformation carrier and, by means of the concatenation, all the sectorsin the buffer can accessed, the mean access time is reduced with a lowoutlay.

The invention is explained in more detail below with reference toexemplary embodiments in drawings.

In the figures:

FIG. 1 shows a block diagram of a reproduction apparatus having a bufferfor reducing the mean access time,

FIG. 2 shows a schematic sketch of the logical arrangement of sectoraddresses in a buffer,

FIG. 3 shows a physical arrangement of sectors in a track bufferaccording to an ascending storage address,

FIG. 4 shows a schematic sketch concerning the relationship between thelogical arrangement of the sectors and the control thereof,

FIG. 5 shows a schematic sketch of an exemplary allocation of a trackbuffer,

FIG. 6 shows a table for illustrating alterations of the allocation ofthe track buffer in the initialization phase,

FIG. 7 shows a table for illustrating alterations of the allocation ofthe track buffer in the initialization phase with representation of theconcatenation,

FIG. 8 shows a table for illustrating alterations of the allocation ofthe track buffer with additional variables, and

FIG. 9 shows a table for illustrating alterations of the allocation ofthe track buffer with an altered entry point.

FIG. 1 illustrates the block diagram of a reproduction apparatus havinga buffer for reducing the mean access time to an information carrier.The reproduction apparatus is a DVD reproduction apparatus, for example,in which, by means of a pick-up PU, also referred to as a read head,sectors S of the optical information carrier are scanned and providedvia a track buffer TB, used as buffer or cache, to an application memoryAM, which is also used for controlling the track buffer TB in thisexemplary embodiment. In order to request sector numbers PSN of theinformation carrier, a control unit CU is provided, which controls thepick-up PU for finding the sector S required by an application.

If an application in the application memory AM requests the reading of asector S, the application initially looks up in a control table CS inthe application memory AM to see whether the sector S is already presentin the track buffer TB. If the sector S is not present in the trackbuffer TB, the application communicates a command for reading the sectorS to the control unit CU, which issues to the pick-up PU a sector readcommand for reading the sector S with the correspondingly predeterminedphysical sector number PSN. The pick-up PU jumps to the correspondinglocation of the optical information carrier and reads this sector S,carries out an ECC decoding and writes the sector S to a free sector Sof the track buffer TB. This ensures that the requested sector S issituated in the track buffer TB, which is then accessed a number oftimes in order to reduce the mean access time. The application in theapplication memory AM then accesses this sector S stored in the trackbuffer TB.

For controlling the allocation of the track buffer TB and for findingsectors S stored in the track buffer TB, the control table CS providedin the application memory AM contains a row or series of endlesslyconcatenated place holders PH and three variables la, lf and lu.

For writing sectors S to the track buffer TB and for a multiple accessto a sector S in the track buffer TB, a track buffer TB is providedwhich, as illustrated in FIG. 2, comprises logically concatenatedstorage locations. Each storage location is assigned a place holder PHwith which the track buffer TB is logically divided into three regions,a region AS for allocated sectors S, a region FS for released sectors Sand a region US for unallocated sector locations. Sectors S in theregion AS of allocated sectors S are sectors S which are used by anapplication in the application memory AM. Sectors S in the region FS ofreleased sectors S are not used by any application in the applicationmemory AM and as yet no sectors have been read into the regions US ofunallocated sector locations by the pick-up PU. The region US ofunallocated sector locations generally represents only an initial state,since gradually there are ever fewer unallocated storage or sectorlocations available and the track buffer TB finally only comprises aregion AS of allocated sectors S and a region FS of released sectors S.A logical combination of the place holders PH is provided, which, bymeans of corresponding numbering, takes account of the successiveregions AS, FS and US, so that a regions AS for allocated sectors Swhich extends from 0 to k−1 is followed by a region FS of k to m⁻¹ forreleased sectors S and a region US of m to n−1 for unallocated sectorlocations. With the concatenation provided, every sector location, in aring arrangement, has a logical next sector location. However, asillustrated in FIG. 3, this logical next sector location need notnecessarily be the next sector location in physical terms as well. Inprinciple, however, the first sector S in the region AS is thetemporally last allocated sector S, the second sector S in the region ASis the temporally penultimate allocated sector S, etc. and the lastsector S in the region of allocated sectors AS points to the firstsector S in the region for released sectors FS. The first sector S inthe region FS for released sectors S is the temporally last releasedsector S, the second sector S in the region FS for released sectors S isthe temporally penultimate released sector S, etc. and the last sector Sin the region FS for released sectors S points to the first sector S inthe region US for unallocated sector locations.

The sectors S in the region US for unallocated sector locations do notrequire a particular order. A simple order would be, for example, thephysical arrangement in the memory, i.e. an order according to anascending storage address. However, in order to close the ring, the lastsector S in the region US for unallocated sector locations must point tothe first sector S in the region AS of allocated sectors S.

A physical arrangement of the sectors S in the track buffer TB accordingto an ascending storage address, i.e. the physical arrangement of thesectors S in the track buffer TB, is illustrated in FIG. 3. In FIGS. 2and 3, the logical combination of the individual sectors S is symbolizedby arrows. The physical order of the sectors S, which is0<r<r+1<s<s+1<t<u, for example, deviates from the logical order of thesectors S, which is identified by 0<k−1<k<m−1<m<n−1. The relationshipbetween the logical order of the sectors S and the physical arrangementthereof in the track buffer TB, which also makes it possible to find thestorage location assigned to a sector number in the track buffer TB, isrealized by a control table CS which is provided in the applicationmemory AM and contains the variables la, lf, lu. As illustrated in anexample in FIG. 4, the first variable la comprises the storage addressindex of the first allocated sector S in the track buffer TB, the secondvariable lf comprises the storage address index of the first releasedsector S in the track buffer TB, while the third variable lu designatesthe storage address index of the first unallocated sector location S inthe track buffer TB. In this exemplary embodiment, the respective firstsector S in the regions AS, FS and US is chosen as entry point into therespective region AS, FS, US. In accordance with one embodiment, thenumber of sectors S in the regions AS, FS and US can be specified withadditional variables na, nf and nu, which, however, are not necessary inprinciple if the variables la, lf, lu are given the opportunity to showthat they do not identify a valid index value. In the example specifiedin FIG. 4, the number of allocated sectors S is equal to seven,resulting in a corresponding variable na=7. The variables nf and nucorrespondingly identify the number of sectors S in the region FS and inthe region US, here being nf=6 and nu=7. The relationship between alogical order LOR of the sectors S and a physical order of the sectors Saccording to an ascending storage address in the track buffer TB, as isrepresented in the control table CS with the corresponding place holdernumber PHN, is illustrated in the lower region of FIG. 4. Arrows andnumber are used to illustrate the assignment. In accordance with theembodiment illustrated, use is made of a storage address indexing 0 to19 whose consecutive numbering corresponds to the consecutive numbering0 to 19 of the logical order LO of the place holders or sectors S,thereby producing a combination between the storage location or itsstorage address index and a subsequent entry with the index next to thenext sector S or place holder PH. By way of example, let the value ofthe variable lf, which identifies the location of the first sector S inthe region FS of released sectors S, be lf=6, so that this determinesthat the first sector S of the region FS of released sectors S issituated at the place holder number PHN=6. This is the number 7 in thelogical order LOR. The entry at the place holder number PHN=6 or theindex next which points to the subsequent place holder PH is next: 9. Atthe place holder number PHN=9, the number of the logical order LOR isthe number 8, so that a logical combination of the sectors S stored inthe track buffer TB is thereby produced despite a physical disorder.

The conditions under which the entries next: x need not be altered andthe cases in which the entries next: x are altered will be illustratedwith reference to examples illustrated in FIGS. 6 to 9.

FIGS. 6 to 9 illustrate two tables which demonstrate by way of examplethe allocation of the track buffer TB with six storage locations and thecorresponding mapping in the series of place holder numbers PHN in thecontrol table CS over a period of time running from top to bottom. Eachof the rows Z from 1 to 15 corresponds in each case to a change in theallocation of the track buffer TB, which, in accordance with theexamples illustrated in FIGS. 6 to 9, is intended to have six placeholders PH with the place holder numbers PHN 0 to 5. Since the index ofthe sectors S, in a loop, is always intended to point to the followingsector S, what is expediently chosen as a starting point for the placeholders PH is an indexing next which beings with a one, risesconsecutively and has a zero at the end of the series of place holdersPH, as illustrated in the first row Z=1 in FIGS. 7 and 8. Since, at thebeginning, no sector S has yet been written to the track buffer TB andnone of the place holders PH is allocated, the result for the variablesla, lf, lu, na, ng, nu illustrated in FIG. 8 is that, except for thevariable nu, which specifies the number of unallocated sectors S bynu=6, all the other variables la, lf, lu, na, nf are equal to zero. RowZ=2 of the tables specifies that, at the place holder PHN=0, a sector Swas written to the track buffer TB, which receives the index 1. In thecontrol table CS, which contains the corresponding storage address indexas first three variables la, lf, lu, that is then mapped in such a waythat la=0, since the sector S is stored at the place holder numberPNH=0. The first released sector S, which is intended to follow theregion AS of allocated sectors is then the sector S which is situated atthe place holder number PNH=1. However, the place holder number PHN=1 isalso the first unallocated sector S, so that the variable lu is likewiselu=1. The number of allocated sectors S is equal to one and isrepresented by the variable na=1. No sector S has hitherto been storedin the region FS of free sectors S, so that the number of the variablenf is correspondingly nf=0. By virtue of the fact that a sector has beenwritten to the track buffer TB, the number of sectors S in the region USof unallocated sector locations has decreased to five in accordance withthe variable nu=5, which can also be determined by the equationnu=6−na−nf. In the third row Z=3, a sector S has again been written tothe track buffer TB, which receives the index 0 on account of theconcatenation provided. The index next of the sector S previouslywritten in becomes next=2 since the first released or unallocated sectorS is now situated at the place holder number PHN=3. The variable la=1 inthe third row specifies that the first allocated sector S is situated atthe location with the place holder number PHN=1. The entry index next: 0of the next place holder PH at the place holder number PHN=2 specifiesthat the next allocated sector S is situated at the place holder numberPHN=0. As a result, the logical combination of the sectors S is producedand the writing of sectors S at unallocated or released storagelocations is controlled and access to the sectors S is also enabled,even though logically they are arranged in a single row. In FIGS. 6 to9, the transitions of the alterations of the allocation of the placeholders PH are specified by designations in#, del#, ru# exclusively forexplanation purposes. A numeral following the designations in#, del#,ru# identifies the place holder number PHN to which the alterationrelates. In detail, the designations in#, del#, ru# identify:

Designation in# specifies that a sector S is written to the track bufferTB at the place holder number PHN specified by the following numeral.

The designation ru# specifies that a sector S still contained in thetrack buffer TB is used again, and

-   -   the designation del# specifies that the corresponding sector S,        at the location identified by the place holder number PHN with        the numeral, is no longer used by any application. However, this        sector S is not erased from the track buffer TB, but rather is        preserved therein until it is overwritten by a new sector S or        is used again.

Since the total number of sectors S in the track buffer TB is known,being 6 in this example, it holds true in principle that na+nf+nu=6. Thesystem thus contains redundancy. In other words, one of the threevariables na, nf, nu in the exemplary embodiment in accordance with FIG.8 can be omitted. By way of example, the variable nu can be completelyreplaced by the formula nu=6−na−nf.

FIG. 6 specifies an exemplary embodiment in which those variables na, nfand nu which identify the number of sectors S in the regions AS, FS, USare not necessary. By the same token, the three variables la, lf and luare given the opportunity to indicate that they do not identify a validindex value. Such states are identified by an asterisk * in FIGS. 6, 7and 9. This asterisk * can be realized e.g. in that a value which doesnot correspond to a possible index value, that is to say all valuesexcept for the 1, 2, 3, 4 and 5 used, indicates that this variable isinvalid. Thus, in the examples, the asterisk * could be realized e.g. bythe number −1 or 6. This exemplary embodiment therefore also representsone of the preferred embodiments since the initialization of the nextpointers of the as yet unallocated place holders PH is additionallydispensed with. This is identified by empty place holders PH in FIG. 6and in FIG. 9. The initialization of the as yet unallocated placeholders PH can be omitted if use is made of the rule that, in the eventof a new allocation of an as yet unallocated placed holder PH, inprinciple the place holder PH with the lowest index is used. For theexample in FIG. 6, this means that the unallocated place holders PH areto be allocated from left to right. Only the next pointer of a newlyallocated place holder PH is initialized. This procedure obviates atime-consuming initialization of all the place holders PH upon newcreation of the control table CS. Nevertheless, fundamentally there isno departure from the principle of the concatenated place holders PH.This is illustrated in FIG. 7, which is identical to FIG. 6 except forthe difference that the allocation or the indices of the unallocatedplace holders PH are specified.

The proposed solution is a buffer with a reduced extent of necessarystorage space for controlling the buffer, and it is even possible toswitch off the cache dynamically.

A description is given above of a special sector cache method which isbased on a row of place holders PH which indicates a place holder PH inthe cache for each sector S. Each place holder PH comprises a pointer tothe location of its sector S in the cache and the index of the nextplace holder PH in the row of place holders PH, resulting in a closedchain which is realized with index values assigned to place holdernumbers PHN.

The method proposed requires only the setting-up of the place holders PHand the three variables la, lf and lu. It is necessary merely toallocate memory for the place holders PH, a 4-byte word, for example,being sufficient for a place holder PH, and it is necessary toinitialize the variables la, lf and lu.

A practical exemplary embodiment of the allocation of the track bufferTB in a DVD reproduction apparatus is illustrated in FIG. 5. The sectorsS illustrated in FIG. 5 contain files of a DVD data stream recorded on aDVD. By way of example, if an application has requested first the fileVIDEO_TS.IFO in the sub-directory VIDEO_TS of an application and thenthe file VTS_(—)01.0.IFO in the same directory, then the file managerrepresenting the application must look up twice in the same directoryVIDEO_TS to find out where this file VIDEO_TS.IFO is situated. In thiscase, the cache can avoid repeated access to the pick-up PU by theapplication first looking up in the cache to see whether the directoryVIDEO_TS is still present there. If so, the application can thendirectly access the sector S of the directory in the track buffer TB.The access to the corresponding sectors S in the track buffer TB isfaster than the access via the pick-up PU and the mean access time isreduced.

FIG. 9 specifies a further exemplary embodiment, in which a sector Spreceding the region AS, FS, US is used as entry point into the regionsAS, FS and US. The variables la, lf, lu, which identify the first sectorS in the respective region AS, FS, US in the other exemplaryembodiments, here point with their entry to the respective last sector Sor place holder PH in the preceding region AS, FS, US. This reduces thenumber of jumps required for alteration of the indexes in the series ofplace holders PH, as becomes clear for example in the transition of theallocation of the place holders PH in row Z=10 to an allocation of theplace holders PH corresponding to row Z=11. The embodiments describedhere are specified only as examples and a person skilled in the art canrealize other embodiments of the invention which remain within the scopeof the invention.

1. Reproduction apparatus having a buffer for reducing the mean accesstime to an information carrier, wherein, for writing sectors to thebuffer and for finding sectors in the buffer, a control table with anumber of place holders and three variables is provided and the placeholders in each case point with an index (next) to a subsequent placeholder in a single endless chain of place holders organized in acircular manner, which is divided into three regions assigned forallocated sectors, released sectors and unallocated sectors, for whichone of the variables respectively identifies a predetermined entry pointinto one of the regions.
 2. Reproduction apparatus according to claim 1,wherein the control table is arranged in an application memory. 3.Reproduction apparatus according to claim 1, wherein the place holdersare provided in the sectors written to the buffer.
 4. Reproductionapparatus according to claim 1, wherein the buffer is a track buffer. 5.Reproduction apparatus according to claim 1, wherein the three variablesand only the place holder with the lowest index (next) are initializedin the initialization phase of the control table.
 6. Reproductionapparatus according to claim 1, wherein, in the case of an arrangementof the place holders in the application memory, each storage location ofthe buffer is assigned a place holder.
 7. Reproduction apparatusaccording to claim 1, wherein the three regions of the endless chain ofplace holders are a region of allocated sectors, a region of releasedsectors and a region of unallocated sectors.
 8. Reproduction apparatusaccording to claim 1, wherein a variable is provided for pointing to afirst sector in a region of allocated sectors, a variable is providedfor pointing to a first sector in a region of released sectors, and avariable is provided for pointing to a first sector in a region ofunallocated sectors, which form a predetermined entry point into therespective region.
 9. Reproduction apparatus according to claim 1,wherein the sectors in a region of unallocated sectors are provided in amanner deviating from a chained order, with the exception of the lastsector, which points to the first sector in a region of allocatedsectors, in the region of unallocated sectors.
 10. Reproductionapparatus according to claim 1, wherein the sectors in the regions arechained with one another in an order corresponding to the temporal orderin which they were written to the buffer.
 11. Reproduction apparatusaccording to claim 1, wherein in each case the sector or place holderwhich precedes the respective region in the chain and is the last sectorof the preceding region is provided as predetermined entry point intoone of the regions with one of the variables.
 12. Reproduction apparatusaccording to claim 1, wherein in each case a sector which is situatedafter a predetermined number of sectors or place holders in the order ofthe sectors in the respective region is provided as predetermined entrypoint into one of the regions with one of the variables.